In this specification and in the annexed claims “relatively movable parts” relates to devices having parts that are relatively movable through relative linear or relative rotational movement or a combination thereof. “Reciprocating piston device” includes compressors and other pressurizing devices as well as engines having relatively movable piston and cylinder irrespective which element is stationary and which element is movable.
In previously known devices having relatively movable parts, and in particular reciprocating piston devices such as piston compressors, normally a sealing arrangement is provided wherein at least one sealing ring is positioned in a circumferential groove at the outside of the piston or in the cylinder in order to provide a seal between the movable piston and the cylinder wall. In particular in respect of piston compressors working with moderate or high pressure the working life of the sealing arrangement before exchange or service is highly dependent on wear of the seal ring as well as wear of the meeting surface of the cylinder wall or rod. This is particularly noticeable in oil-free compressors.
Excessive wear of the sealing ring and subsequent failure of the sealing arrangement results in need for replacement and/or service. As a consequence, this leads to a period of downtime of a device including the sealing arrangement such as a compressor together with related machines during the replacement time. Altogether this results in increased costs and discontinued production or operation. The corresponding problems occur in other reciprocating piston devices and shafts as intended in this specification.
As an example of background art, FR-1 543 403 may be mentioned. Herein pressure acting on the inside of a number of piston rings is limited by means of a valve arrangement.
In sealing arrangements for relatively rotational members such as e.g. rotary shaft sealing arrangements corresponding problems occur, in particular the problems are important if there is a great pressure difference between the sides of the sealing arrangement.